MIT researchers augment humans with extra robotic arms


July 2, 2014

MIT researchers are developing extra robot limbs that can help out humans where an extra hand, arm, or leg might be useful

MIT researchers are developing extra robot limbs that can help out humans where an extra hand, arm, or leg might be useful

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Featured in comic books since 1963, Dr. Octopus, or "Doc Ock" is an enemy of Spiderman with four extra robotic arms attached to his back that assist him in his nefarious plans. That vision of humans with extra limbs – minus the supervillain part – is taking shape at MIT with researchers adding "supernumerary robotic arms" to assist with tasks that ordinary two-armed humans would find difficult.

There are many tasks around the house or factory that you have probably said to yourself, “if I only an extra arm, this would be a lot easier." Tasks like hanging a ceiling fan, installing an overhead light fixture, or even just holding open a box would be easier if there was an extra arm to help out. Now engineers are envisioning two robotic arms as helping hands.

The project is being run at MIT’s d'Arbeloff Laboratory for Information Systems and Technology and headed by Federico Parietti and Baldin Llorens-Bonilla, both in the Mechanical Engineering Department. Federico has been working on lower limbs, bracing strategies, and stability, while Baldin contributed to the robot shoulder arms, along with coordination and task planning.

The concept was demonstrated with installing ceiling panels in an airplane, a task that must be duplicated dozens of times in the construction of an airliner. A single person installing a large panel overhead must struggle between holding the panel to the ceiling, inserting screws into holes, and using a powered screwdriver to attach the panel. The juggling and dropping of screws would drive any of us to frustration and profanity.

The Supernumerary Robot Limbs (SRL) team looked at this task, and added two lightweight robot arms to a frame attached to a backpack. The arms are attached directly over the spine so that the body can carry the extra weight without strain. This alone would be noteworthy, except that the user now has no way to command the robot arms to move – a conventional joystick or gamepad would take up hands already busy with panels.

So the amazing part of this research is having the arms decide for themselves when and where to help. Sensors on the human’s wrists and on the robot mount determine where the human is on the task, and assigns the robot arms to help.

The robot arms assist the user by pushing up the panel against the ceiling, allowing the human operator to put in screws to attach the panel. As the panel is able to support itself, first one arm goes down, and then the other as the robot senses that the force required to maintain the pose has diminished.

The arms are programmed by the "teach by demonstration" method. A second human first demonstrates to the robot how to help by moving the robot arms manually with the the robot remembering this lesson so it is then able to make the moves on its own.

Another application studied by the group is using arms attached to the wearer’s waist that can automatically add stability. Imagine a construction worker trying to drill a hole in a beam while working on a new skyscraper a hundred meters in the air, standing on another beam a few centimeters or inches wide. The supernumerary arms attached to the waist would grab the beams for support and act as stabilizers, attaching the worker to the structure at two points, just like having two extra arms to hold on with.

Each of the robot’s limbs can sense the applied torque, and modify its movements accordingly. Besides just passively holding panels in position, the robot arms can also assist with more precision tasks, like guiding a drill to a particular spot. The research team spent a lot of time developing specific techniques for computing where the robot arms can best assist, and deciding where the robot arms can best be attached for support.

The project is being supported in part by Boeing, hence the interest in aircraft assembly, but the team sees a range of potential applications for the technology. These include assisting senior citizens, construction workers, and other assembly operators where extra arms might come in (pardon the phrase) handy.

"We want our design to be as light and ergonomic as possible without compromising the robot’s power and capabilities," says Baldin.

The current design is the third generation of robot arms developed, with the shoulder arms weighing about 11-12 lbs. (5-5.4 kg). The team is planning further development of the concept to reduce weight, increase strength, and improve coordination by "developing better control algorithms and increasing the sensing capabilities of the robot."

The video below shows the robotic limbs being demonstrated installing ceiling panels in an airplane.

Sources: MIT d’Arebeloff Laboratory for Information Systems and Technology, Federico Parietti, Baldin Llorens-Bonilla

About the Author
Francis X Govers III Francis Govers is the designer of over 20 land, sea, air and space vehicles and teaches robotics and the design of self-driving cars. He spent 10 years at NASA, helped design the International Space Station, participated in the DARPA Grand Challenge, and managed the only Zeppelin operating in the US. As a commercial pilot, writer, artist, musician, engineer, race car nut and designer, Francis has a serious addiction to building things that frequently gets him into trouble. All articles by Francis X Govers III

Come on Zevulon, they're talking about "Doc Oc". I think this is a super cool idea. However, I agree with others who have mentioned a more direct control of the arms might be better. A neural link between the user and the interface would make this one of the coolest things I've ever seen! I guess it didn't work out well for the doctor though...

Bryan Rule

I saw something similar in a cartoon when I was a kid. Exo suits could make one guy fly another, another roll and another swim underwater. cool stuff. I hope this tech get perfected. it will make projects easier to do.


Simple way to overcome this is to have a toggle with three modes of arm operation: 1. Manual put into position, so you use your human arm to drag the robot arm to where it is mean to hold, then lock into position 2. lock, where the arm stays in the position it is last orientated, with all joints and rotation immobile (including claw) 3. Mimic, where sensors on real arms dictate movement, and the robot arm follows.

An independent toggle for each arm between the three states will likely provide 99% of all requirements.

Autonomous movement is fraught with danger as it relies on contextual understanding of what is going on, and likely going to end up hurting the end user (flailing robot arms anyone?). With the obvious exception of multipurpose heads, like mechanical screwdrivers and cutting tools that are moved through mode (3), and their function started by voice command, e.g. "left hand, screwdriver, clockwise, start"


Haven't any of these engineers ever read a Spiderman comic? This is not going to end well.

Francois Retief

This could be awesome once mind control is added. I have often argued long hand hard that If I could have one thing extra it would be a Tail ... with a hand attached. This could be the next best thing.


ummm.... you need to make it thought controlled! I'm too lazy to have to teach a robot to do what I need, figure out how to make it thought controlled and you have a winner...

If other scientist can figure out how to get a robotic prosthetic arm to move by thought, I think MIT can figure it out also...


Umm.. Yes, it is cool. Very cool. But essentially impractical. That's a lot of hardware to strap on, walk around in, and maintain.

How is this more efficient than using a climbing belt to hang from something or using an extension pole with a flat hunk of wood screwed to it to brace an overhead panel?

Maneuvering around a working office space in that rig would be awkward. Wearing a tool belt and carrying a pole is much easier and less disruptive.


i'm left wondering where is the spiderman technology in this. should this guy have gecko pads and be shooting quick dry gluesilk out of his mouth or something?


This is not Spider Tech for it really is Octopus Technology, although it really needs more than two additional arms; maybe 4, 6, or 12 additional arms. How about 2, 4, 6 or 12 additional legs to help climb, run or leap better. The military would love to have soldiers who can carry, lift and shoot more. In construction one would have to put up 4x8 foot sheets of dry wall, but in the video it shows a person holding up a small sheet of plastic; not great feat there. Although, every journey begins with a single step. We are definitely entering into the age of Robotics.

Kristianna Thomas

The human skeleton is only so strong would it be able to stand the strain????

Dave Ussery

The human mind has "interfaces" for 4 limbs. So even if the tech was developed enough to control these mechanical limbs by way of a neural link, the operator might not be able to control them while still having use of his "built in" limbs. So probably not Dr. Octopus as much as super Vise Grips. Not as glamorous but still very useful & worth the effort & expense to develop.


An early starting point, hopefully it will get more versatile with user feedback. Another story comes to mind - anybody else remember (I think it was by Niven) written about bio-modified chimps with extra arms/hands instead of legs - designed for weightless (space station) construction and maintenance?

The Skud

It's a great idea, which promises great prospects in different areas of our life. For example, it might be of interest to owners of large harems. Well, to be serious, I think it will be applicable in those areas where the achievement of the final objective is based on the verge of strength and talent. For instance, it can become an assistant to the sculptor, cabinetmaker ...

Rafael Kireyev

Seems like a lot of complication for the applications they cite. For the ceiling panel installation, a movable personal overhead scaffold on wheels would seem to be just as easy, less complicated and less expensive. Plus unlike arms, it could have shelves and bins for holding tools and fasteners. And it would put zero strain on the back, while the arms still force the back to carry the weight of the ceiling panels. You can walk away if you need to get something and the panel would remain in place, unlike if you were using the arms. For the stability function, just use a safety harness. Window washers have used them for many decades.

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